This specification relates to quantum computing systems. A variety of quantum computing systems and techniques have been proposed. A quantum computing system may include a quantum information processor, a communication interface, data storage, and other features. A quantum processor typically encodes information in the state of a quantum system and utilizes the dynamics of the quantum system to process the encoded information. In some contexts, such devices can execute computing tasks by controlling, manipulating, or otherwise utilizing the quantum dynamics of the system. In addition, quantum computing systems may encrypt quantum information and store or communicate the encrypted quantum information. In some examples, encrypted quantum information can be communicated between separate quantum computing systems (e.g., between clients and servers).